The selection of a green colorant for foods leaves one with limited choices. One can either use an FD&C color or chlorophyll. Unfortunately, the FD&C color stains carpets and fabric heavily and irreversibly. And, the color imparted by chlorophyll changes to an unappetizing "khaki" green under acid conditions. The same is true of various chlorophyll derivatives such as copper chlorophyllin.
Chlorophyllin is an umbrella term that includes several breakdown products of chlorophyll saponification with either sodium or potassium hydroxide, resulting in sodium chlorophyllin or potassium chlorophyllin.
These compounds have the advantage over chlorophyll in that they are water soluble. Unfortunately, the molecule includes a magnesium atom which is easily removed at low pH, causing the color to turn brownish.
The color of chlorophyllin can be made more acceptable by subjecting it to a strong mineral acid treatment to strip out the magnesium and replace it with copper. The resulting copper chlorophyllin has a green hue and is stable at low pH. Unfortunately it precipitates out of solution under acid conditions.
Copper chlorophyllin is known to be available in two commercial forms. One (sold by Dr. Marcus, GmbH) is an acid-stable liquid comprised of 3% copper chlorophyllin, 24% polysorbate 80 and 73% water. The solution has an alkaline pH at which solubility is not a problem. The other (sold by Meer Corp.) is a powder of 100% copper chlorophyllin.
In U.S. Pat. No. 4,187,320, Koch, et al., identify copper 30 chlorophyllin as a pigment useful in chewing gum bases. The form of the pigment is not mentioned. The pH is not disclosed, but it would seem to be alkaline due to the presence of filler materials such as calcium carbonate, and the like.
In U.S. Pat. No. 5,112,600, Jackson, et al., describe an anti-caries composition containing a source of hydrogen citrate ions and having a pH of from 4 to 7. Among the additives are "chlorophyll compounds (e.g., sodium copper chlorophyllin)". Again, the physical form is not identified.
Moreover, the purpose of adding the sodium copper chlorophyllin is apparently for purposes other than color and no example of its use in liquid form is given.
Similarly, in U.S. Pat. No. 5,709,873, Bar-Shalom, et al., disclose dental compositions in which copper chlorophyllin is listed as a source of chlorophyll. Again, the purpose does not appear to be for color, and no detail is provided of a specific application.
In U.S. Pat. No. 5,209,978, Kosaka, et al., list copper chlorophyllin as one of several dyes suitable for coloring gelatin capsules. No pH or physical form information are given.
There remains a need for an acid-stable and cold-water-soluble form of green color based on non-staining copper chlorophyllin. The new compositions should be in the form of dry, free-flowing powders that wet easily and dissolve rapidly and completely in aqueous liquids having acid pH values suitable for fruity-flavored beverages and foods such as gelatin desserts.